Two early-evening clusters

Rigel, the brightest star in the constellation Orion, crosses the Meridian near 8 pm.   To the east of Orion lies Jupiter, currently the brightest object in the evening sky.  Farther to the east are two star clusters, M44 and M67, that are better positioned for viewing a couple hours later.  

In the image below, M44 (the "Beehive Cluster") is circled.  M67 lies about 8 deg to the south of M44. Equipment: Olympus E-M1iii + Leica 9mm f/1.7 + Hoya Sparkle-6 filter.

View toward the SSE. 8 pm.

 The sky brightness at 10 pm was sqml=19.73–77, an improvement from recent nights.

M44, the Beehive Cluster.  40 sec, ISO 1600. 2.4-deg-wide FOV.

 This image of M44 (and M67 below) was obtained with the AT72EDII refractor and a Metabones 0.71x Speedbooster, for a final focal length of 307mm at f/4.3.  The camera was an Olympus E-M5iii.

M67. 1-deg FOV.

 M67, also known as the "Golden Eye Cluster", is one of the oldest open clusters in our galaxy.  It is about 4.5 billion years old, about the same age as the Sun.  At one time it was speculated that our sun may have originated in this cluster, but that is now thought to be unlikely.

M67, 2-deg FOV.  Rokinon 135mm f/2 + Olympus E-M5.

 

Leica 9mm + Sparkle-6 filter.  9:16 pm 08 Feb.

M44 and M67

Sirius, the Dog Star

 The brightest star in the night sky is Sirius.  As the brightest star in the constellation Canis Major (the Great Dog), it is also known as the Dog Star.

The waning Snow Moon is now rising late enough to provide a period of darkness in the early evening for testing lenses.  The newest lens is a Rokinon AF 75mm f/1.8 FE for Sony E-mount cameras.  The following images were obtained with this lens on a Sony A7iii camera.  Exposures were between 20 and 30 sec at ISO 1600.  The measured sky brightness was sqml=19.58 mpsas.

Sirius and Canis Major.  Hoya Sparkle-6 filter.

 

Hoya Softon-A filter.

Sometimes the diffraction pattern produced by the Sparkle-6 filter is too obtrusive.  In those cases the Softon filter provides a more natural aesthetic.  Unfortunately, the Softon filter does not preserve red star colors as well.  

Orion.  Softon-A filter.

Messier 41 (M41) is a nice open star cluster that lies about 4 deg south of Sirius.  These two image crops help to demonstrate the relative color response of the two filters. Note especially the trio of reddish stars to the right between Sirius and M41.

Hoya Sparkle-6 filter.

Hoya Softon-A filter.

Three Rokinon lenses.  The new 75mm lens is on the right.

Rokinon is the brand label used for Samyang lenses in the North American market, although the same lens is frequently available with either label from the same vendor.

Active Sun: 3 Feb

 There is a large sunspot group generating strong flares that may produce geomagnetic storms.  There are also many large prominences visible along the limb of the sun (in Hydrogen-alpha light).

White light.  Orion 80mmED + front filter.

 

Hydrogen-Alpha light.  Lunt LS50THa double-stacked.

false-color Hydrogen-Alpha.

The Sun and the Snow Moon

 The full moon of February is traditionally known as the "Snow Moon".  This year it occurred on Sunday, 1 February.  

Snow Moon rising

Snow Moon.  Orion 80mmED refractor.

There is a large active sunspot group rotating into view on the Sun:

Orion 80mmED with front-mounted solar filter.

 

2x enlargement

Star clusters at two focal lengths

 The sky brightness has been poor the last couple nights, with a measured value of sqml=19.38 mpsas.  There appears to be a very thin cloud or haze layer, but it is clear enough to experiment with some star-cluster photography.

Equipment used: Rokinon 135mm f/2 lens with an Olympus E-M5, and a SkyWatcher SkyMax 102 MCT with a Sony A7iii.  Exposures were limited to between 20 and 30 sec because of the sky brightness.

M36 (LL) and M38 (UR) in Auriga.  Rokinon 135mm + E-M5, 20 sec.

 The Olympus E-M5 is the original version, bought new in 2012, so this is a 14-year-old camera.  At the time, this was a game-changer in the micro-four-thirds format.  It is still a good camera, but no longer my first choice for astrophotography.

M35 in Gemini.  Rokinon 135mm. 20 sec.

 The SkyMax 102 has a nominal focal length of 1300 mm, not quite ten times longer than the Rokinon.  The fully illuminated image circle from this scope is about 22 mm, slightly smaller than the 24mm height of the Sony "full-frame" sensor.  This corresponds to about a 1-deg FOV.

M35. SkyMax 102, 1300mm, 30 sec.

 There is a smaller and dimmer cluster to the lower right of M35.  This is NGC 2158.  It appears much smaller because it is almost six times farther away.

NGC 2158 at 135mm.  4x enlargement.

 

NGC 2158 at 1300 mm.

The limiting magnitude in both images is in the range of 14.5–15.  The 1300-mm image obviously has higher resolution.

 

M37 in Auriga.  SkyMax 102, 1300 mm, 20 sec.

Hyperion: a dim and distant moon of Saturn

 Saturn currently has 274 known moons, ranging in size from planet-like Titan to others that are essentially large rocks less than a mile wide.  Last night (16 Jan) a SkyWatcher SkyMax 102 Maksutov-Cassegrain telescope was used to track down Hyperion, the eighth largest moon of Saturn.  Hyperion has an irregular shape, with its longest dimension being about 224 mi (360 km).  It is a dim moon with a visual magnitude of 14+.

The sky looked clear at 7:30 pm, but as darkness increased a thin cloud layer was visible.  This increased the difficulty of an otherwise successful capture of Hyperion.

The SkyMax 102 has a nominal focal length of 1300 mm and an aperture of 102 mm (4 in.).  It was used with an Olympus E-M5iii camera.

Five of Saturn's largest moons.  20 sec, ISO 1600.

 

Hyperion to the left of overexposed Saturn.  30 sec, ISO 1600.

Predicted moon positions.  Credit: SkySafariAstronomy.com

The SkyMax 102 was also used with a front-mounted solar filter to image some large sunspots currently traversing the sun:

16 Jan

 

17 Jan

With this telescope the sun's projected image barely fits on the micro-four-thirds sensor.

Moons of Saturn

 The Astro-Tech AT72EDII refractor, with it's 430 mm focal length and meager 72mm (2.8") aperture, is not an ideal planetary telescope.  In the not-so-dark skies of urban Santa Fe it is better suited to photographing or observing star clusters or the Moon and Sun.  However, it is fun to see what can be done with it.  So far it has picked up two moons of Uranus (Titania and Oberon) and a dim and distant moon of Jupiter (Himalia), none of which I had seen before.

Last night the scope was turned to Saturn, Neptune, and the dwarf-planet Ceres.

The current locations of Ceres, Neptune, and Saturn.  (credit: SkySafariAstronomy.com)

 Five moons of Saturn were visible in a 20-sec exposure:

 Four of the moons, Titan, Rhea, Dione, and Tethys are in a line with Saturn's ring plane.  The rings are hidden in the glare of the overexposed planet and are currently nearly edge-on.  A fifth moon, Iapetus, sits just above Saturn accompanied by a background field star.

Credit: SkySafariAstronomy.com

 Neptune is a more difficult target.  Last night, its largest moon Triton was separated by only 11 arcseconds from the planet.  It appears to be just-barely visible in a 5-sec exposure:

Neptune and Triton. 3x enlargement.

 

Credit: SkySafariAstronomy.com

 At magnitude 13.8, Triton requires a fairly large telescope to be observed visually.  It is about 77% the diameter of our Moon, and is larger than the dwarf-planet Pluto.

Ceres is the closest dwarf planet to Earth, orbiting in the main asteroid belt between Mars and Jupiter.  It is currently at magnitude 9, about the same as Saturn's moon Titan.

Ceres (circled).  1-deg FOV (vertical).

 The sky brightness last night was sqml=19.68, which is an improvement from the previous few days.  

Some more star-cluster pictures:

M34 in Perseus. 1-deg FOV.  30-sec exposure.

 

NGC 1582 in Perseus.  20-sec exposure.

M37 in Auriga.  25-sec exposure.